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Bacterium-like particles (BLPs) have gained significant attention in vaccine development due to their potential as effective immune enhancers and antigen delivery systems. BLPs are generated by boiling lactic acid bacteria in an acidic solution and are devoid of proteins and nucleic acids, offering advantages in terms of ease of preparation, high safety, and good stability. Furthermore, by employing protein anchor (PA), heterogeneous antigens can be efficiently displayed on the surface of BLPs, resulting in enhanced delivery effectiveness. Despite these benefits, most BLP-based vaccines are currently administered via injection or intranasal delivery, with oral delivery remaining limited. This limitation is primarily due to the harsh environment of the gastrointestinal tract, which degrades the antigens displayed on the surface of these particles. To enhance the efficacy of oral immunization with subunit vaccines, we developed a simple and rapid method for self-assembling a lipid membrane onto the surface of BLPs vaccines, achieving an encapsulation efficiency of up to 99%, and the combination has good biosafety. The novel oral delivery system not only preserves the adjuvant activity of BLPs but also efficiently protects antigens from adverse gastrointestinal environments, increasing the absorption of the vaccine in intestinal Peyer's patches (PPs). Oral immunization was required only once, and protection after the challenge was up to 100%. Furthermore, we observed rapid immunity and cross-protection. Transcriptome analysis of the small intestine suggested that immune enhancement probably be exerted by promoting the absorption and transport of antigens. Therefore, we posit that the design of this new oral delivery system presents a novel approach to advancing the development of oral subunit vaccines. [ABSTRACT FROM AUTHOR]

A new synthesized Schiff base, N-((anthracen-9-yl) methylene-2-methyl benzenamine) (AMMB), was prepared from o-toluidine and 9-anthracenecarboxaldehyde. The structure of the compound was confirmed by single crystal X-ray diffraction and characterized through various analytical tools such as high resolution mass, 1H and 13C NMR, infrared, UV-vis and elemental composition analysis. The molecular geometries of AMMB were optimized by means of DFT/B3LYP/6311-G++ (d,p) basis set. The optimized geometric parameters of the compound were concordant with the single crystal structure. The optimized structure was utilized in comparison of experimental FT-IR with calculated frequency calculation. TD-DFT analysis was performed to compute the electronic absorption of the compound. SCF-GIAO was employed to compute 1H and 13C NMR, which was consistent with the experimental results. Additionally, NLO, NBO, MEP and global reactivity parameters were also computed using the same level of theory. Hirshfield surface analysis, fingerprint plot and energy frameworks were presented to explore the intermolecular interactions within the crystal. Molecular docking study was carried out to predict the probable binding site of AMMB into lipid bilayers such as DMPC, DPPC, POPC, DLPE, DOPC and POPE. The molecular docking analysis of AMMB showed complex formation with binding affinity energy ranging from −9.3 to −3.4 kcal/mol. [ABSTRACT FROM AUTHOR]

[Display omitted] Nonionic surfactant aerosols play a crucial role in many industries, but they can cause acute irritation to users' eyes during spraying. This cytotoxic process is associated with corneal cell necrosis causing cell membrane disruption. Industrial grade surfactants are typically polydisperse mixtures described by their nominal chemical structure but how the polydispersity affects their interactions with cell membrane, remains largely unexplored. A better understanding could benefit product formulations to maximise their efficiency whilst minimising their toxicity to the users. In this study, poly - oxyethylene glycol monododecyl ethers (C 12 E 4 , C 12 E 23) were used to form ideal binary surfactant mixtures. The cytotoxicities of mono and polydispersed surfactants towards human corneal epithelial cells were examined, followed by a series of biophysical characterisations of interactions between surfactants and model cell membranes. Notably, to probe the journey of individual C 12 E 4 and C 12 E 23 surfactant molecules across the cell membrane from a binary surfactant mixture, "two-colour" neutron reflection measurements were achieved via Hydrogen/Deuterium substitution. The relative distributions of C 12 E 4 and C 12 E 23 across cell membranes and their nanostructural conformations revealed a synergistic membrane-lytic ability initiated by surfactant mixing, with the more hydrophobic C 12 E 4 exhibiting stronger membrane binding potency than the hydrophilic C 12 E 23. The exact molar ratio of C 12 E 4 against C 12 E 23 in the mixture determined how the mixed surfactant interacted with the cell membrane, and how the process directly impacted cytotoxicity and eye irritation. Thus, the cytotoxicity of polydisperse surfactants is not the same as monodisperse surfactant of the same average structure. This work provides a useful basis for the assessment of surfactant mixing by balancing their efficiency and toxicity. [ABSTRACT FROM AUTHOR]

Modeled after biological neurons, neuristors are emerging hardware that generate recurring voltage spikes in response to electrical stimulation. This type of excitability can enable transistor‐free spiking neural networks for efficient signal processing and computing. Yet, most neuristors consist of circuits containing numerous devices, thus complicating fabrication and increasing size, power usage, and cost. In contrast, it is shown that a single, 5nm‐thick lipid membrane functionalized with voltage‐activated peptides functions as a two‐terminal, ultra‐low power (fW‐pW) artificial neuristor in response to supplied current. Specifically, the biomolecular membrane generates stochastic voltage oscillations (10–150 mV) in response to direct currents (|5–40| pA), and is capable of generating two distinct types of action potentials fast (≈1–50 ms) and slow (≈1–2 s) spikes via distinct physical mechanisms. This discovery showcases the inherent multifunctionality and modularity of engineered biomembranes, and it contributes to an expanding suite of ionic and biomolecular devices designed with synapse and neuron functionalities for emerging computing architectures. [ABSTRACT FROM AUTHOR]

The SARS-CoV-2 E protein is an enigmatic viral structural protein with reported viroporin activity associated with the acute respiratory symptoms of COVID-19, as well as the ability to deform cell membranes for viral budding. Like many viroporins, the E protein is thought to oligomerize with a well-defined stoichiometry. However, attempts to determine the structure of the protein complex have yielded inconclusive results, suggesting several possible oligomers, ranging from dimers to pentamers. Here, we combined patch-clamp, confocal fluorescence microscopy on giant unilamellar vesicles, and atomic force microscopy to show that E protein can exhibit two modes of membrane activity depending on membrane lipid composition. In the absence or the presence of a low content of cholesterol, the protein forms short-living transient pores, which are seen as semi-transmembrane defects in a membrane by atomic force microscopy. Approximately 30 mol% cholesterol is a threshold for the transition to the second mode of conductance, which could be a stable pentameric channel penetrating the entire lipid bilayer. Therefore, the E-protein has at least two different types of activity on membrane permeabilization, which are regulated by the amount of cholesterol in the membrane lipid composition and could be associated with different types of protein oligomers. [ABSTRACT FROM AUTHOR]

In the realm of parasitology, autophagy has emerged as a critical focal point, particularly in combating Leishmaniasis. Central to this endeavour is the recognition of the protein ATG8 as pivotal for the survival and infectivity of the parasitic organism Leishmania major, thereby making it a potential target for therapeutic intervention. Consequently, there is a pressing need to delve into the structural characteristics of ATG8 to facilitate the design of effective drugs. In this study, our efforts centered on the purification of ATG8 from Leishmania major, which enabled novel insights into its structural features through meticulous spectroscopic analysis. We aimed to comprehensively assess the stability and behaviour of ATG8 in the presence of various denaturants, including urea, guanidinium chloride, and SDS-based chemicals. Methodically, our approach included secondary structural analysis utilizing CD spectroscopy, which not only validated but also augmented computationally predicted structures of ATG8 reported in previous investigations. Remarkably, our findings unveiled that the purified ATG8 protein retained its folded conformation, exhibiting the anticipated secondary structure. Moreover, our exploration extended to the influence of lipids on ATG8 stability, yielding intriguing revelations. We uncovered a nuanced perspective suggesting that targeting both the lipid composition of Leishmania major and ATG8 could offer a promising strategy for future therapeutic approaches in combating leishmaniasis. Collectively, our study underscores the importance of understanding the structural intricacies of ATG8 in driving advancements towards the development of targeted therapies against Leishmaniasis, thereby providing a foundation for future investigations in this field. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid plaques in the brain. The toxicity of amyloid to neuronal cell surfaces arises from interactions between small intermediate aggregates, namely amyloid oligomers, and the cell membrane. The nature of these interactions changes with age and disease progression. In our previous work, we demonstrated that both membrane composition and nanoscale structure play crucial roles in amyloid toxicity, and that membrane models mimicking healthy neuron were less affected by amyloid than model membranes mimicking AD neuronal membranes. This understanding introduces the possibility of modifying membrane properties with membrane-active molecules, such as melatonin, to protect them from amyloid-induced damage. In this study, we employed atomic force microscopy and localized surface plasmon resonance to investigate the protective effects of melatonin. We utilized synthetic lipid membranes that mimic the neuronal cellular membrane at various stages of AD and explored their interactions with amyloid- β (1–42) in the presence of melatonin. Our findings reveal that the early diseased membrane model is particularly vulnerable to amyloid binding and subsequent damage. However, melatonin exerts its most potent protective effect on this early-stage membrane. These results suggest that melatonin could act at the membrane level to alleviate amyloid toxicity, offering the most protection during the initial stages of AD. [ABSTRACT FROM AUTHOR]

Bacterium-like particles (BLPs) have gained significant attention in vaccine development due to their potential as effective immune enhancers and antigen delivery systems. BLPs are generated by boiling lactic acid bacteria in an acidic solution and are devoid of proteins and nucleic acids, offering advantages in terms of ease of preparation, high safety, and good stability. Furthermore, by employing protein anchor (PA), heterogeneous antigens can be efficiently displayed on the surface of BLPs, resulting in enhanced delivery effectiveness. Despite these benefits, most BLP-based vaccines are currently administered via injection or intranasal delivery, with oral delivery remaining limited. This limitation is primarily due to the harsh environment of the gastrointestinal tract, which degrades the antigens displayed on the surface of these particles. To enhance the efficacy of oral immunization with subunit vaccines, we developed a simple and rapid method for self-assembling a lipid membrane onto the surface of BLPs vaccines, achieving an encapsulation efficiency of up to 99%, and the combination has good biosafety. The novel oral delivery system not only preserves the adjuvant activity of BLPs but also efficiently protects antigens from adverse gastrointestinal environments, increasing the absorption of the vaccine in intestinal Peyer’s patches (PPs). Oral immunization was required only once, and protection after the challenge was up to 100%. Furthermore, we observed rapid immunity and cross-protection. Transcriptome analysis of the small intestine suggested that immune enhancement probably be exerted by promoting the absorption and transport of antigens. Therefore, we posit that the design of this new oral delivery system presents a novel approach to advancing the development of oral subunit vaccines.

Understanding interactions of inorganic nanoparticles with biomolecules is important in many biotechnology, nanomedicine, and toxicological research, however, the size of typical nanoparticles makes their direct modeling by atomistic simulations unfeasible. Here, we present a bottom‐up coarse‐graining approach for modeling titanium dioxide (TiO 2) nanomaterials in contact with phospholipids that uses the inverse Monte Carlo method to optimize the effective interactions from the structural data obtained in small‐scale all‐atom simulations of TiO 2 surfaces with lipids in aqueous solution. The resulting coarse‐grained models are able to accurately reproduce the structural details of lipid adsorption on different titania surfaces without the use of an explicit solvent, enabling significant computational resource savings and favorable scaling. Our coarse‐grained simulations show that small spherical TiO 2 nanoparticles (r=2 nm) can only be partially wrapped by a lipid bilayer with phosphoethanolamine headgroups, however, the lipid adsorption increases with the radius of the nanoparticle. The current approach can be used to study the effect of the size and shape of TiO 2 nanoparticles on their interactions with cell membrane lipids, which can be a determining factor in membrane wrapping as well as the recently discovered phenomenon of nanoquarantining, which involves the formation of layered nanomaterial–lipid structures. [ABSTRACT FROM AUTHOR]

Immobilization of biomaterials is a very important task in the development of biofuel cells and biosensors. Some semiconducting metal-oxide-based supporting materials can be used in these bioelectronics-based devices. In this article, we are reviewing some functionalization methods that are applied for the immobilization of biomaterials. The most significant attention is paid to the immobilization of biomolecules on the surface of semiconducting metal oxides. The improvement of biomaterials immobilization on metal oxides and analytical performance of biosensors by coatings based on conducting polymers, self-assembled monolayers and lipid membranes is discussed. [ABSTRACT FROM AUTHOR]

Calmodulin (CaM) is a ubiquitous calcium-sensitive messenger in eukaryotic cells. It was previously shown that CaM possesses an affinity for diverse lipid moieties, including those found on CaM-binding proteins. These facts, together with our observation that CaM accumulates in membrane-rich protrusions of HeLa cells upon increased cytosolic calcium, motivated us to perform a systematic search for unmediated CaM interactions with model lipid membranes mimicking the cytosolic leaflet of plasma membranes. A range of experimental techniques and molecular dynamics simulations prove unambiguously that CaM interacts with lipid bilayers in the presence of calcium ions. The lipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) hold the key to CaM–membrane interactions. Calcium induces an essential conformational rearrangement of CaM, but calcium binding to the headgroup of PS also neutralizes the membrane negative surface charge. More intriguingly, PE plays a dual role—it not only forms hydrogen bonds with CaM, but also destabilizes the lipid bilayer increasing the exposure of hydrophobic acyl chains to the interacting proteins. Our findings suggest that upon increased intracellular calcium concentration, CaM and the cytosolic leaflet of cellular membranes can be functionally connected.

Abstract Chemokines are cytokines whose primary role is cellular activation and stimulation of leukocyte migration. They perform their various functions by interacting with G protein-coupled cell surface receptors (GPCRs) and are involved in the regulation of many biological processes such as apoptosis, proliferation, angiogenesis, hematopoiesis or organogenesis. They contribute to the maintenance of the homeostasis of lymphocytes and coordinate the function of the immune system. However, chemokines and their receptors are sometimes hijacked by some pathogens to infect the host organism. For a given chemokine receptor, there is a wide structural, organizational and conformational diversity. In this review, we describe the evidence for structural variety reported for the chemokine receptor CCR5, how this variability can be exploited by HIV-1 to infect its target cells and what therapeutic solutions are currently being developed to overcome this problem.

Experimental studies reveal that the anionic lipid phosphatidic acid (POPA), non-phospholipid cholesterol, and cationic lipid DOTAP inhibit the gating of voltage-sensitive potassium (Kv) channels. Here, we develop a continuum electromechanical model to investigate the interaction of these lipids with the ion channel. Our model suggests that: (i) POPA lipids may restrict the vertical motion of the voltage-sensor domain through direct electrostatic interactions; (ii) cholesterol may oppose the radial motion of the pore domain of the channel by increasing the mechanical rigidity of the membrane; and (iii) DOTAP can reduce the effect of electrostatic forces by regulating the dielectric constant at the channel–lipid interface. The electromechanical model predictions for the three lipid types match well with the experimental observations and provide mechanistic insights into lipid-dependent gating of Kv channels.

The catalytic properties of cytochrome c (Cc) have captured great interest in respect to mitochondrial physiology and apoptosis, and hold potential for novel enzymatic bioremediation systems. Nevertheless, its contribution to the metabolism of environmental toxicants remains unstudied. Human exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with impactful diseases, and animal models have unveiled concerning signs of PAHs' toxicity to mitochondria. In this work, a series of eight PAHs with ionization potentials between 7.2 and 8.1 eV were used to challenge the catalytic ability of Cc and to evaluate the effect of vesicles containing cardiolipin mimicking mitochondrial membranes activating the peroxidase activity of Cc. With moderate levels of H2O2 and at pH 7.0, Cc catalyzed the oxidation of toxic PAHs, such as benzo[a]pyrene, anthracene, and benzo[a]anthracene, and the cardiolipin-containing membranes clearly increased the PAH conversions. Our results also demonstrate for the first time that Cc and Cc–cardiolipin complexes efficiently transformed the PAH metabolites 2-hydroxynaphthalene and 1-hydroxypyrene. In comparison to horseradish peroxidase, Cc was shown to reach more potent oxidizing states and react with PAHs with ionization potentials up to 7.70 eV, including pyrene and acenaphthene. Spectral assays indicated that anthracene binds to Cc, and docking simulations proposed possible binding sites positioning anthracene for oxidation. The results give support to the participation of Cc in the metabolism of PAHs, especially in mitochondria, and encourage further investigation of the molecular interaction between PAHs and Cc. [ABSTRACT FROM AUTHOR]

Lipid droplets are organelles responsible for the accumulation and breakdown of neutral fats in the human body. Lipid droplets have a monolayer shell of phospholipids, which prevents their spontaneous fusion. The fusion of lipid droplets is carried out by specialized fusion proteins and is regulated by the lipid composition of the monolayer membrane. The efficiency of fusion is determined by the energy needed for the local approach of lipid droplets and the topological rearrangement of their monolayers. In this work, the fusion of monolayers is modeled within the framework of the theory of membrane elasticity. The energy barrier for fusion is calculated under various conditions simulating possible compositions of monolayers, as well as the possible effects of proteins. The calculation results show that the height of the barrier is most dependent on the distance between lipid droplets, which is determined by the fusion proteins. Lipid composition also affects the fusion efficiency and can change it several tens of times, which is consistent with previously obtained data on bilayer fusion. [ABSTRACT FROM AUTHOR]

The thickness of the lipid membrane is its substantial characteristics. Usually, the thickness of a lipid bilayer is experimentally determined by measuring its electrical capacitance in the approximation of a plane-parallel capacitor. However, membranes formed from a mixture of lipids or containing membrane-deforming inclusions are laterally inhomogeneous, and for them the plane-parallel capacitor approximation generally does not hold. In this work, corrections to the electrical capacitance resulting from deformation of the lipid membrane were numerically calculated. It is shown that the model of a planar capacitor (or their parallel connections), in the general case, does not quantitatively describe these corrections due to the non-zero tangential component of the electric field strength. It is shown that the relative deviation of corrections to the electrical capacitance calculated in various simplified models from the exact solution can reach 50%. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are one of the elements of innate immunity that have a crucial role in fighting infections. These molecules are produced by all kinds of cells and can display a wide spectrum of action against bacterial or fungal infections. Bacterial resistance toward broad‐spectrum antibiotics has become a major concern in recent years. In this context, AMPs have emerged as promising alternative therapy in response to this increasing problem because of their ability to inhibit growth and biofilm formation, even in drug‐resistant microorganisms. However, despite the myriad of patents filed related to AMPs, only a small proportion of AMPs have already received certification, either by the Food and Drug Administration (FDA) or European Medicines Agency (EMA). In order to pave the way of AMPs to certification, a comprehensive knowledge of the mechanism of action of these peptides is essential. Several models have been proposed to explain it and the permeabilization of the bacterial envelope seems to play a key role in most of them. In this review, we describe the different techniques that are generally used to assess the permeabilization induced by AMPs in either in vivo or in vitro systems. Additionally, a comprehensive analysis of the cooperation during the process of binding and permeabilization is included. [ABSTRACT FROM AUTHOR]

Desiccation presents considerable challenges to the survival of various bacteria, disrupting cellular functions and damaging the structure of macromolecular assemblies. Dehydration can induce a phase transition in lipid membranes, shifting from a favorable fluid phase to an unfavorable gel-like structure. In response to this stress, various organisms evolve different types of protective mechanisms, among which an accumulation of disaccharides is particularly noteworthy. Despite large number studies are present in the literature, the detailed mechanism of how disaccharides mitigate the deleterious effect of desiccation on lipid membrane is still elusive. Our study examines how disaccharides, like sucrose and trehalose, protect lipid membranes derived from an Escherichia coli (E. coli) bacteria during desiccation, aiming to uncover the mechanisms behind membrane protection and its significance for bacterial survival. We have simulated the lipid membrane at six different hydration levels, ranging from fully hydrated (with a water-to-lipid ratio of 42) to severely dehydrated (with a ratio of 2), both in the presence and absence of sucrose. We monitor various structural and dynamical parameters of the lipid membrane with a reduction of the hydration level. We conduct a comparative analysis between sucrose and trehalose. Our findings indicate that dehydration negatively impacts the fluidity of the membrane, and both the disaccharides demonstrate nearly equal effectiveness in mitigating the adverse effects of extreme dehydration on the lipid membrane. Furthermore, we provide evidence supporting the validity of the vitrification and water replacement hypotheses in understanding the role of disaccharides in protecting lipid membranes.

Our study successfully fabricated sourness and saltiness sensors and investigated the response toward acetic acid and sodium chloride as the sourness and saltiness sample solutions, respectively. The sensors were made using a lipid membrane with a mixture of two materials. The fabricated sensors can detect the concentration of a small amount of 0.03 mM for the sourness sensor and 0.316 mM for the saltiness sensor, much lower than the human tongue threshold. Moreover, the sensors show a directly proportional response for both sourness and saltiness sensors in the range of 0.03–3 mM of acetic acid and 0.316–31.6 mM of sodium chloride, respectively. The interaction between positive charge in the lipid membrane and anionic species in the sample solution was believed to be the sensing mechanism in this research. Both sensors were refabricated three times, and the saltiness sensor exhibited a similar response when exposed to 3.16 mM of sodium chloride, while the sourness sensor still has to improve its reproducibility. In addition, the fabricated sensors were also tested on three consecutive days to observe the stability.

Exosomes are cell-secreted vesicles less than ≈150 nm in size that contain gene-encoding and gene-silencing RNA and cytosolic proteins with roles in intercellular communication. Interest in the use of exosomes as targeted drug delivery vehicles has grown since it was shown that they can bind specific cells and deliver intact genetic material to the cytosol of target cells. We isolated extracellular vesicles (EVs), consisting of a mixture of exosomes and microvesicles, from prostate (PC3) and melanoma (M21) cancer cell lines using serial ultracentrifugation. Interrogation via western blot analysis confirmed enrichment of CD63, a widely recognized EV surface protein, in the EV pellet from both cell lines. Nanoparticle tracking analysis (NTA) of EV pellets revealed that the two cell lines produced distinct vesicle size profiles in the ≈30 nm to ≈400 nm range. NTA further showed that the fraction of exosomes to all EVs was constant, suggesting cellular mechanisms that control the fraction of secreted vesicles that are exosomes. Transmission electron microscopy (TEM) images of the unmodified PC3 EVs showed vesicles with cup-like (i.e., nanocapsule) and previously unreported prolate morphologies. The observed non-spherical morphologies for dehydrated exosomal vesicles (size ≈30-100 nm) are most likely related to the dense packing of proteins in exosome membranes. Solubility phase diagram data showed that EVs enhanced the solubility of paclitaxel (PTX) in aqueous solution compared to a water-only control. Combined with their inherent targeting and cytosol delivery properties, these findings highlight the potential advantages of using exosomes as chemotherapeutic drug carriers in vivo.

The SARS-CoV-2 E protein is an enigmatic viral structural protein with reported viroporin activity associated with the acute respiratory symptoms of COVID-19, as well as the ability to deform cell membranes for viral budding. Like many viroporins, the E protein is thought to oligomerize with a well-defined stoichiometry. However, attempts to determine the structure of the protein complex have yielded inconclusive results, suggesting several possible oligomers, ranging from dimers to pentamers. Here, we combined patch-clamp, confocal fluorescence microscopy on giant unilamellar vesicles, and atomic force microscopy to show that E protein can exhibit two modes of membrane activity depending on membrane lipid composition. In the absence or the presence of a low content of cholesterol, the protein forms short-living transient pores, which are seen as semi-transmembrane defects in a membrane by atomic force microscopy. Approximately 30 mol% cholesterol is a threshold for the transition to the second mode of conductance, which could be a stable pentameric channel penetrating the entire lipid bilayer. Therefore, the E-protein has at least two different types of activity on membrane permeabilization, which are regulated by the amount of cholesterol in the membrane lipid composition and could be associated with different types of protein oligomers.

Thickness of lipid bilayer membranes is a key physical parameter determining membrane permeability and stability with respect to formation of through pores. Most membrane inclusions or impurities like amphipathic peptides, transmembrane peptides, lipid inclusions of a different molecular shape, lipid domains, and protein-lipid domains, locally deform the membrane. The detailed structure of the locally deformed region of the membrane is a kind of "fingerprint" for the inclusion type. However, most experimental methods allow determining only averaged parameters of membranes with incorporated inclusions, thus preventing the direct obtaining of the characteristics of the inclusion. Here we developed a model that allows the obtaining of characteristic parameters of three types of membrane inclusions (amphipathic peptides, transmembrane peptides, monolayer lipid patches) from experimentally observable dependencies of the average thickness of lipid bilayer on the surface concentration of the inclusions. In the case of amphipathic peptides, the model provided the peptide parameters that were in qualitative agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

Matrix vesicles are a special class of extracellular vesicles thought to actively contribute to both physiologic and pathologic mineralization. Proteomic studies have shown that matrix vesicles possess high amounts of annexin A5, suggesting that the protein might have multiple roles at the sites of calcification. Currently, Annexin A5 is thought to promote the nucleation of apatitic minerals close to the inner leaflet of the matrix vesicles' membrane enriched in phosphatidylserine and Ca2+. Herein, we aimed at unravelling a possible additional role of annexin A5 by investigating the ability of annexin A5 to adsorb on matrix-vesicle biomimetic liposomes and Langmuir monolayers made of dipalmitoylphosphatidylserine (DPPS) and dipalmitoylphosphatidylcholine (DPPC) in the absence and in the presence of Ca2+. Differential scanning calorimetry and dynamic light scattering measurements showed that Ca2+ at concentrations in the 0.5–2.0 mM range induced the aggregation of liposomes probably due to the formation of DPPS-enriched domains. However, annexin A5 avoided the aggregation of liposomes at Ca2+ concentrations lower than 1.0 mM. Surface pressure versus surface area isotherms showed that the adsorption of annexin A5 on the monolayers made of a mixture of DPPC and DPPS led to a reduction in the area of excess compared to the theoretical values, which confirmed that the protein favored attractive interactions among the membrane lipids. The stabilization of the lipid membranes by annexin A5 was also validated by recording the changes with time of the surface pressure. Finally, fluorescence microscopy images of lipid monolayers revealed the formation of spherical lipid-condensed domains that became unshaped and larger in the presence of annexin A5. Our data support the model that annexin A5 in matrix vesicles is recruited at the membrane sites enriched in phosphatidylserine and Ca2+ not only to contribute to the intraluminal mineral formation but also to stabilize the vesicles' membrane and prevent its premature rupture. [ABSTRACT FROM AUTHOR]

Due to the stimulation of neuronal membrane dipoles by action potentials, under suitable conditions coherent dipole oscillations can be formed. We argue that these dipole oscillations satisfy the weak Bose-Einstein condensate criteria of the Froehlich model of biological coherence. They can subsequently generate electromagnetic fields (EMFs) propagating in the inter-neuronal space. When neighboring neurons fire synchronously, EMFs can create interference patterns and hence form holographic images containing analog information about the sensory inputs that trigger neuronal activity. The mirror pattern projected by EMFs inside the neuron can encode information in the neuronal cytoskeleton. We outline an experimental verification of our hypothesis and its consequences for anesthesia, neurodegenerative diseases, and psychiatric states.

Soft matter systems exhibit diversity and intricacy in their structures and properties, with their dynamic behaviors and structural changes spanning wide time and length scales. Gaining insight into the internal structures and dynamics behaviors of soft matter systems, as well as the interactions among molecules and particles, contributes to a deeper comprehension of the microscopic behaviors of matter. Moreover, this endeavor has significant biomedical and materials engineering implications. This review focuses on the applications of spin-echo small-angle neutron scattering (SESANS) and high-resolution neutron spin echo (NSE) spectroscopy in soft matter science, particularly complex fluids and biomolecular systems. NSE spectroscopy has remarkable temporal resolution and sensitivity towards molecular-scale dynamic behaviors. Therefore, it provides comprehensive insights into microscale dynamic phenomena to soft matter systems, such as the rheological behaviors, stability, and aggregation dynamics of colloids; the domain dynamics and conformational changes of proteins; the collective dynamics of lipid membranes and interactions with other molecules, as well as the dynamic behaviors and interactions of surfactants within microemulsions. NSE technique helps reveal the complex nature of these systems, providing valuable insights into advances in materials science, biomedicine, and chemistry.

The principles of the electronic tongue sensor include potentiometry using a type of electrode with a liquid junction design. Mint leaves are widely used in the industrial sector in food, beverage, and medicinal products. In the industrial sector there are obstacles in the quality control process when analyzing the content in beverage products, in which the tools are unable to accurately classify the ingredients in the product. The content of a mixture of mint and tea was tested using seven working electrodes coated with different lipid membranes and classified using principal component analysis (PCA) and linear discriminant analysis (LDA). The electronic tongue was tested on a solution representing the five basic tastes. The accuracy of the readings of each sensor was obtained using a support vector regression (SVR) linear model with the mean absolute error (MAE) equal to 0.43 and a correlation coefficient ( R 2 ) of 0.93. [ABSTRACT FROM AUTHOR]

Lutein, zeaxanthin, and meso-zeaxanthin (a steroisomer of zeaxanthin) are macular pigments. They modify the physical properties of the lipid bilayers in a manner similar to cholesterol. It is not clear if these pigments are directly present in the lipid phase of the membranes, or if they form complexes with specific membrane proteins that retain them in high amounts in the correct place in the retina. The high content of macular pigments in the Henle fiber layer indicates that a portion of the lutein and zeaxanthin should not only be bound to the specific proteins but also directly dissolved in the lipid membranes. This high concentration in the prereceptoral region of the retina is effective for blue-light filtration. Understanding the basic mechanisms of these actions is necessary to better understand the carotenoid–membrane interaction and how carotenoids affect membrane physical properties—such as fluidity, polarity, and order—in relation to membrane structure and membrane dynamics. This review focuses on the properties of lutein. [ABSTRACT FROM AUTHOR]

All biological phenomena can be classified as open, dissipative and non-linear. Moreover, the most typical phenomena are associated with non-linearity, dissipation and openness in biological systems. In this review article, four research topics on non-linear biosystems are described to show the examples from various biological systems. First, membrane dynamics of a lipid bilayer for the cell membrane is described. Since the cell membrane separates the inside of the cell from the outside, self-organizing systems that form spatial patterns on membranes often depend on non-linear dynamics. Second, various data banks based on recent genomics analysis supply the data including vast functional proteins from many organisms and their variable species. Since the proteins existing in nature are only a very small part of the space represented by amino acid sequence, success of mutagenesis-based molecular evolution approach crucially depends on preparing a library with high enrichment of functional proteins. Third, photosynthetic organisms depend on ambient light, the regular and irregular changes of which have a significant impact on photosynthetic processes. The light-driven process proceeds through many redox couples in the cyanobacteria constituting chain of redox reactions. The fourth topic focuses on a vertebrate model, the zebrafish, which can help to understand, predict and control the chaos of complex biological systems. In particular, during early developmental stages, developmental differentiation occurs dynamically from a fertilized egg to divided and mature cells. These exciting fields of complexity, chaos, and non-linear science have experienced impressive growth in recent decades. Finally, future directions for non-linear biosystems are presented. [ABSTRACT FROM AUTHOR]

Cellular engulfment and uptake of macromolecular assemblies or nanoparticles via endocytosis can be associated to both healthy and disease-related biological processes as well as delivery of drug nanoparticles and potential nanotoxicity of pollutants. Depending on the physical and chemical properties of the system, the adsorbed particles may remain at the membrane surface, become wrapped by the membrane, or translocate across the membrane through an endocytosis-like process. In this paper, we address the question of how the wrapping of colloidal particles by lipid membranes can be controlled by the shape of the particles, the particle–membrane adhesion energy, the membrane phase behavior, and the membrane-bending rigidity. We use a model system composed of soft core–shell microgel particles with spherical and ellipsoidal shapes, together with phospholipid membranes with varying composition. Confocal microscopy data clearly demonstrate how tuning of these basic properties of particles and membranes can be used to direct wrapping and membrane deformation and the organization of the particles at the membrane. The deep-wrapped states are more favorable for ellipsoidal than for spherical microgel particles of similar volume. Theoretical calculations for fixed adhesion strength predict the opposite behavior— wrapping becomes more difficult with increasing aspect ratio. The comparison with the experiments implies that the microgel adhesion strength must increase with increasing particle stretching. Considering the versatility offered by microgels systems to be synthesized with different shapes, functionalizations, and mechanical properties, the present findings further inspire future studies involving nanoparticle–membrane interactions relevant for the design of novel biomaterials and therapeutic applications. [ABSTRACT FROM AUTHOR]

Hierarchical assembly of building blocks via competing, orthogonal interactions is a hallmark of many of nature's composite materials that do not require highly specific ligand-receptor interactions. To mimic this assembly mechanism requires the development of building blocks capable of tunable interactions. In the present work, we explored the interplay between repulsive (steric and electrostatic) and attractive hydrophobic forces. The designed building blocks allow hydrophobic forces to effectively act at controlled, large distances, to create and tune the assembly of membrane-based building blocks under dilute conditions, and to affect their interactions with cellular membranes via physical cross-bridges. Specifically, we employed double-end-anchored poly(ethylene glycol)s (DEA-PEGs)-hydrophilic PEG tethers with hydrophobic tails on both ends. Using differential-interference-contrast optical microscopy, synchrotron small-angle X-ray scattering (SAXS), and cryogenic electron microscopy, we investigated the ability of DEA-PEGs to mediate assembly in the dilute regime on multiple length scales and on practical time scales. The PEG length, anchor hydrophobicity, and molar fraction of DEA-PEG molecules within a membrane strongly affect the assembly properties. Additional tuning of the intermembrane interactions can be achieved by adding repulsive interactions via PEG-lipids (steric) or cationic lipids to the DEA-PEG-mediated attractions. While the optical and electron microscopy imaging methods provided qualitative evidence of the ability of DEA-PEGs to assemble liposomes, the SAXS measurements and quantitative line-shape analysis in dilute preparations demonstrated that the ensemble average of loosely organized liposomal assemblies maintains DEA-PEG concentration-dependent tethering on defined nanometer length scales. For cationic liposome-DNA nanoparticles (CL-DNA NPs), aggregation induced by DEA-PEGs decreased internalization of NPs by cells, but tuning the DEA-PEG-induced attractions by adding repulsive steric interactions via PEG-lipids limited aggregation and increased NP uptake. Furthermore, confocal microscopy imaging together with colocalization studies with Rab11 and LysoTracker as markers of intracellular pathways showed that modifying CL-DNA NPs with DEA-PEGs alters their interactions with the plasma and endosomal membranes.

An arbitrary Lagrangian–Eulerian (ALE) finite element method for arbitrarily curved and deforming two-dimensional materials and interfaces is presented here. An ALE theory is developed by endowing the surface with a mesh whose in-plane velocity need not depend on the in-plane material velocity, and can be specified arbitrarily. A finite element implementation of the theory is formulated and applied to curved and deforming surfaces with in-plane incompressible flows. Numerical inf–sup instabilities associated with in-plane incompressibility are removed by locally projecting the surface tension onto a discontinuous space of piecewise linear functions. The general isoparametric finite element method, based on an arbitrary surface parametrization with curvilinear coordinates, is tested and validated against several numerical benchmarks. A new physical insight is obtained by applying the ALE developments to cylindrical fluid films, which are computationally and analytically found to be stable to non-axisymmetric perturbations, and unstable with respect to long-wavelength axisymmetric perturbations when their length exceeds their circumference. A Lagrangian scheme is attained as a special case of the ALE formulation. Though unable to model fluid films with sustained shear flows, the Lagrangian scheme is validated by reproducing the cylindrical instability. However, relative to the ALE results, the Lagrangian simulations are found to have spatially unresolved regions with few nodes, and thus larger errors.

An arbitrary Lagrangian–Eulerian (ALE) finite element method for arbitrarily curved and deforming two-dimensional materials and interfaces is presented here. An ALE theory is developed by endowing the surface with a mesh whose in-plane velocity need not depend on the in-plane material velocity, and can be specified arbitrarily. A finite element implementation of the theory is formulated and applied to curved and deforming surfaces with in-plane incompressible flows. Numerical inf–sup instabilities associated with in-plane incompressibility are removed by locally projecting the surface tension onto a discontinuous space of piecewise linear functions. The general isoparametric finite element method, based on an arbitrary surface parametrization with curvilinear coordinates, is tested and validated against several numerical benchmarks. A new physical insight is obtained by applying the ALE developments to cylindrical fluid films, which are computationally and analytically found to be stable to non-axisymmetric perturbations, and unstable with respect to long-wavelength axisymmetric perturbations when their length exceeds their circumference. A Lagrangian scheme is attained as a special case of the ALE formulation. Though unable to model fluid films with sustained shear flows, the Lagrangian scheme is validated by reproducing the cylindrical instability. However, relative to the ALE results, the Lagrangian simulations are found to have spatially unresolved regions with few nodes, and thus larger errors.

Alzheimer's disease is the most common form of dementia. Its aetiology is characterized by the misfolding and aggregation of amyloid-β (Aβ) peptides into β-sheet-rich Aβ oligomers/fibrils. Although multiple experimental studies have suggested that Aβ oligomers/fibrils interact with the cell membranes and perturb their structures and dynamics, the molecular mechanism of this interaction is still not fully understood. In the present work, we have performed a total of 120 μs-long simulations to investigate the interaction between trimeric or hexameric Aβ1–40 fibrils with either a 100% DPPC bilayer, a 70% DPPC-30% cholesterol bilayer or a 50% DPPC-50% cholesterol bilayer. Our simulation data capture the spontaneous binding of the aqueous Aβ1–40 fibrils with the membranes and show that the central hydrophobic amino acid cluster, the lysine residue adjacent to it and the C-terminal hydrophobic residues are all involved in the process. Moreover, our data show that while the Aβ1–40 fibril does not bind to the 100% DPPC bilayer, its binding affinity for the membrane increases with the amount of cholesterol. Overall, our data suggest that two clusters of hydrophobic residues and one lysine help Aβ1–40 fibrils establish stable interactions with a cholesterol-rich DPPC bilayer. These residues are likely to represent potential target regions for the design of inhibitors, thus opening new avenues in structure-based drug design against Aβ oligomer/fibril-membrane interaction.

Subtle variations in the structure and composition of lipid membranes can have a profound impact on their transport of functional molecules and relevant cell functions. Here, we present a comparison of the permeability of bilayers composed of three lipids: cardiolipin, DOPG (1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol), and POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol)). The adsorption and cross-membrane transport of a charged molecule, D289 (4-(4-diethylaminostyry)-1-methyl-pyridinium iodide), on vesicles composed of the three lipids were monitored by second harmonic generation (SHG) scattering from the vesicle surface. It is revealed that structural mismatching between the saturated and unsaturated alkane chains in POPG leads to relatively loose packing structure in the lipid bilayers, thus providing better permeability compared to unsaturated lipid bilayers (DOPG). This mismatching also weakens the efficiency of cholesterol in rigidifying the lipid bilayers. It is also revealed that the bilayer structure is somewhat disturbed by the surface curvature in small unilamellar vesicles (SUVs) composed of POPG and the conical structured cardiolipin. Such subtle information on the relationship between the lipid structure and the molecular transport capability of the bilayers may provide clues for drug development and other medical and biological studies. [ABSTRACT FROM AUTHOR]

Lateral phase separation within lipid bilayer membranes has attracted considerable attention in the fields of biophysics and cell biology. Living cells organize laterally segregated compartments, such as raft domains in an ordered phase, and regulate their dynamic structures under isothermal conditions to promote cellular functions. Model membrane systems with minimum components are powerful tools for investigating the basic phenomena of membrane phase separation. With the use of such model systems, several physicochemical characteristics of phase separation have been revealed. This review focuses on the isothermal triggering of membrane phase separation from a physical point of view. We consider the free energy of the membrane that describes lateral phase separation and explain the experimental results of model membranes to regulate domain formation under isothermal conditions. Three possible regulation factors are discussed: electrostatic interactions, chemical reactions and membrane tension. These findings may contribute to a better understanding of membrane lateral organization within living cells that function under isothermal conditions and could be useful for the development of artificial cell engineering. [ABSTRACT FROM AUTHOR]

Biomolecular phase separation has emerged as an essential mechanism for cellular organization. How cells respond to environmental stimuli in a robust and sensitive manner to build functional condensates at the proper time and location is only starting to be understood. Recently, lipid membranes have been recognized as an important regulatory center for biomolecular condensation. However, how the interplay between the phase behaviors of cellular membranes and surface biopolymers may contribute to the regulation of surface condensation remains to be elucidated. Using simulations and a mean-field theoretical model, we show that two key factors are the membrane's tendency to phase-separate and the surface polymer's ability to reorganize local membrane composition. Surface condensate forms with high sensitivity and selectivity in response to features of biopolymer when positive co-operativity is established between coupled growth of the condensate and local lipid domains. This effect relating the degree of membrane-surface polymer co-operativity and condensate property regulation is shown to be robust by different ways of tuning the co-operativity, such as varying membrane protein obstacle concentration, lipid composition, and the affinity between lipid and polymer. The general physical principle emerged from the current analysis may have implications in other biological processes and beyond. [ABSTRACT FROM AUTHOR]

An effect of receptor‐binding domain (RBD) of SARS‐CoV‐2 S‐protein on structural parameters of model lipid membranes presented by dimyristoylphosphatidylcholine (DMPC) systems with cholesterol and melatonin impurities is studied by small angle neutron scattering (SANS). It is shown that an increase in melatonin concentration in the lipid membrane leads to a decrease in the thickness of the lipid bilayer, while an increase in the concentration of cholesterol leads to an increase in its thickness. It is suggested that increasing the concentration of melatonin in a membrane prevents the interaction of coronaviral S‐protein with a lipid membrane of a cell. In the presence of cholesterol in the system, the interaction of a lipid membrane with an active part of S‐protein occurs depending on a phase state of the lipid: in the case of a gel phase, there is no changes in structural parameters, but at higher temperatures in the case of a liquid crystal phase, an addition of RBD SARS‐CoV‐2 to the system causes a reduce in the membrane thickness. [ABSTRACT FROM AUTHOR]

The catalytic properties of cytochrome c (Cc) have captured great interest in respect to mitochondrial physiology and apoptosis, and hold potential for novel enzymatic bioremediation systems. Nevertheless, its contribution to the metabolism of environmental toxicants remains unstudied. Human exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with impactful diseases, and animal models have unveiled concerning signs of PAHs’ toxicity to mitochondria. In this work, a series of eight PAHs with ionization potentials between 7.2 and 8.1 eV were used to challenge the catalytic ability of Cc and to evaluate the effect of vesicles containing cardiolipin mimicking mitochondrial membranes activating the peroxidase activity of Cc. With moderate levels of H2O2 and at pH 7.0, Cc catalyzed the oxidation of toxic PAHs, such as benzo[a]pyrene, anthracene, and benzo[a]anthracene, and the cardiolipin-containing membranes clearly increased the PAH conversions. Our results also demonstrate for the first time that Cc and Cc–cardiolipin complexes efficiently transformed the PAH metabolites 2-hydroxynaphthalene and 1-hydroxypyrene. In comparison to horseradish peroxidase, Cc was shown to reach more potent oxidizing states and react with PAHs with ionization potentials up to 7.70 eV, including pyrene and acenaphthene. Spectral assays indicated that anthracene binds to Cc, and docking simulations proposed possible binding sites positioning anthracene for oxidation. The results give support to the participation of Cc in the metabolism of PAHs, especially in mitochondria, and encourage further investigation of the molecular interaction between PAHs and Cc.

Lipid domains play a critical role in signal transduction and transport across cell membranes. The formation of domains in “HLC” ternary lipid bilayers composed of high transition temperature (high- Tm ) lipids, low- Tm lipids, and cholesterol (Chol) has been extensively studied as a raft-like system. Recently, experiments were performed to control the formation of submicron domains in LLC lipid bilayers containing low- Tm phosphatidylethanolamine (PE), low- Tm phosphatidylcholine (PC), and Chol by manipulating the presence or absence of Chol. The formation of microdomains in this LLC mixture was replicated by dissipative particle dynamics simulation. The results show that domain formation can be replicated.

An important advance in biosensor research is the extension and application of laboratory-developed methodologies toward clinical diagnostics, though the propensity toward nonspecific binding of materials in clinically relevant matrices, such as human blood serum and plasma, frequently leads to compromised assays. Several surface chemistries have been developed to minimize nonspecific interactions of proteins and other biological components found within blood and serum samples, though these often exhibit substantially variable outcomes. Herein we report a surface chemistry consisting of a charged-matched supported lipid membrane that has been tailored to form over a gold surface functionalized with protein A. Fine tuning of the interfacial charge of this membrane, along with rational selection of a backfilling self-assembled monolayer, allows for high surface coverage with retention of orientation-controlled capture antibody attachment. We demonstrate using surface-plasmon resonance (SPR) that this highly charged lipid membrane is antifouling, allowing for complete removal of nonspecific human serum and plasma components using only a mild buffer rinse, which we attribute to unique steric interactions with the underlying surface. Furthermore, this surface chemistry is successfully applied for specific detection of IgG and cholera toxin in undiluted human biofluids with negligible sacrifice of SPR signal compared to buffered analysis. This novel lipid membrane interface over protein A may open new avenues for direct biosensing of disease markers within clinical samples.

The increase in atmospheric oxygen levels imposed significant environmental pressure on primitive organisms concerning intracellular oxygen concentration management. Evidence suggests the rise of cholesterol, a key molecule for cellular membrane organization, as a cellular strategy to restrain free oxygen diffusion under the new environmental conditions. During evolution and the increase in organismal complexity, cholesterol played a pivotal role in the establishment of novel and more complex functions associated with lipid membranes. Of these, caveolae, cholesterol-rich membrane domains, are signaling hubs that regulate important in situ functions. Evolution resulted in complex respiratory systems and molecular response mechanisms that ensure responses to critical events such as hypoxia facilitated oxygen diffusion and transport in complex organisms. Caveolae have been structurally and functionally associated with respiratory systems and oxygen diffusion control through their relationship with molecular response systems like hypoxia-inducible factors (HIF), and particularly as a membrane-localized oxygen sensor, controlling oxygen diffusion balanced with cellular physiological requirements. This review will focus on membrane adaptations that contribute to regulating oxygen in living systems.

Porphyrins are well-known photosensitizers (PSs) for antibacterial photodynamic therapy (aPDT), which is still an underestimated antibiotic-free method to kill bacteria, viruses, and fungi. In the present work, we developed a comprehensive tool for predicting the structure and assessment of the photodynamic efficacy of PS molecules for their application in aPDT. We checked it on a series of water-soluble phosphorus(V) porphyrin molecules with OH or ethoxy axial ligands and phenyl/pyridyl peripheral substituents. First, we used biophysical approaches to show the effect of PSs on membrane structure and their photodynamic activity in the lipid environment. Second, we developed a force field for studying phosphorus(V) porphyrins and performed all-atom molecular dynamics simulations of their interactions with bacterial lipid membranes. Finally, we obtained the structure-activity relationship for the antimicrobial activity of PSs and tested our predictions on two models of Gram-negative bacteria, Escherichia coli and Acinetobacter baumannii. Our approach allowed us to propose a new PS molecule, whose MIC50 values after an extremely low light dose of 5 J/cm2 (5.0 ± 0.4 μg/mL for E. coli and 4.9 ± 0.8 μg/mL for A. baumannii) exceeded those for common antibiotics, making it a prospective antimicrobial agent.

Despite extensive researches on the motion of polymer chains on lipid membranes, the effect of membrane fluctuations on polymer chain dynamics remains poorly understood. Here we report single molecule tracking experiments that allow for comparable measurements of polymer chain diffusion dynamics on nanotubular and planar phospholipid membranes. We observe a super-diffusion behavior and no apparent chain-length-dependent mobility of polymer chains on nanotubular membranes, while a Brownian motion and apparent chain-length-dependent mobility of polymer chains on planar membranes. We suggest the super-diffusion nature of polymer chains may be due to the thermal-fluctuations of lipid nanotubes, which can be described from a statistical thermodynamic phenomenon coupling of polymer chain dynamics and surface thermal fluctuations. We suggest that the existence of surface environment fluctuations should influence the dynamics of the adsorbed polymer chains. This study provides previously uncharacterized insights into polymer diffusion dynamics on thermal-fluctuating flexible surfaces, which is essential to understanding the effect of environment fluctuations on polymer chain behaviors. [ABSTRACT FROM AUTHOR]

We study morphological transitions of lipid membrane under the presence of the intra-surface viscous flow and membrane thickness dilation using a two-dimensional-based continuum model of Helfrich type. The effects of intra-membrane viscosity and membrane distension are simultaneously formulated into the model of continuum deformation based on the dimension reduction procedure applied to three-dimensional liquid crystal theory. The admissible set of boundary conditions is taken from the existing model yet reformulated into the present context for the sake of completeness. Among other interesting features, the proposed model predicts the off-centred protrusion of the lipid membrane when it is subjected to both local inflammation and intra-surface viscous flow. In addition, the substrate-interaction force may invoke local bending effects on membrane, resulting in thickness reduction in the vicinity of the substrate. Lastly, the obtained results are cross-examined with coarse-grained molecular dynamics simulations which demonstrate reasonable consistency in the predictions of membrane morphology and thickness dilation. [ABSTRACT FROM AUTHOR]

[Display omitted] Designed antimicrobial lipopeptides (ALPs) offer the attractive benefits of short peptide sequences and flexible tuning of amphiphilicity by altering the acyl chain length. These lipopeptides kill microbes by forming intriguing in-membrane nanostructures and causing the leakage of internal contents. However, how subtle differences in the molecular structures of the lipopeptides affect their antimicrobial efficacy and biocompatibility to host cells is still under-investigated. This work focuses on assessing changes in the acyl chain length of CH 3 (CH 2) n-2 CO-KKKIII-NH 2 (n = 10, 12 and 14, K = lysine, I = isoleucine, denoted as C n KI3) on the antimicrobial potency and cytotoxicity by combining biological assays with physical measurements. Aggregation properties were characterized by changes in critical aggregation concentration (CAC) from surface tension measurements. Antimicrobial susceptibility tests, cytotoxic MTT assays, haemolytic tests, and dynamic bactericidal experiments were employed to reveal their bioactive potency toward different types of cells. To further investigate lipopeptides' underlying antimicrobial and cytotoxic mechanisms, lipid monolayer and lipid small unilamellar vesicle (SUV) models were established and biophysically characterized. An increase in n led to the decrease in the CAC of C n KI3, showing a rising membrane-lytic power. Subsequent bioactive measurements revealed the optimal performance of C 12 KI3 from this series of lipopeptides. The selective membrane binding behaviour was well supported by neutron reflection data from charged lipid monolayer models, revealing membrane-supported nanostructures of ALPs. However, increased membrane-lytic actions in C 14 KI3 led to notably increased toxicity and reduced selectivity. On the other hand, C 14 KI3 can impose faster dynamic killing than natural lipopeptide polymyxin B, showing the distinct impact of the amphiphilic balance from the designed lipopeptide. In contrast, the distinctly weaker binding to zwitterionic membrane models (monolayers and SUVs) provided direct nanoscale structural evidence to the mildness of the designed ALPs on host cells. This work demonstrates the high selectivity and fast killing of rationally designed short ALPs to microbes via in-membrane nanostructuring. [ABSTRACT FROM AUTHOR]

Reproducing the dynamics of proteins and/or nucleic acids in a solution in which microdroplets of the similar size as cells or organelles are emerged by liquid-liquid phase separation, is an excellent model system. This is a powerful and rewarding strategy for understanding the properties of living cells. The targets of that research also include the formation of membraneless organelles, which has been gaining more attention in recent years. Here, the current results of our research using representative biopolymers, actin cytoskeleton and DNA, and phospholipids that are important components of biological membranes, would be introduced. [ABSTRACT FROM AUTHOR]

Abstract Background Nanoplastics have been recently found widely distributed in our natural environment where ubiquitously bacteria are major participants in various material cycles. Understanding how nanoplastics interact with bacterial cell membrane is critical to grasp their uptake processes as well as to analyze their associated risks in ecosystems and human microflora. However, little is known about the detailed interaction of differentially charged nanoplastics with bacteria. The present work experimentally and theoretically demonstrated that nanoplastics enter into bacteria depending on the surface charges and cell envelope structural features, and proved the shielding role of membrane lipids against nanoplastics. Results Positively charged polystyrene nanoplastics (PS-NH2, 80 nm) can efficiently translocate across cell membranes, while negatively charged PS (PS-COOH) and neutral PS show almost no or much less efficacy in translocation. Molecular dynamics simulations revealed that the PS-NH2 displayed more favourable electrostatic interactions with bacterial membranes and was subjected to internalisation through membrane penetration. The positively charged nanoplastics destroy cell envelope of Gram-positive B. subtilis by forming membrane pore, while enter into the Gram-negative E. coli with a relatively intact envelope. The accumulated positively charged nanoplastics conveyed more cell stress by inducing a higher level of reactive oxygen species (ROS). However, the subsequently released membrane lipid-coated nanoplastics were nearly nontoxic to cells, and like wise, stealthy bacteria wrapped up with artifical lipid layers became less sensitive to the positively charged nanoplastics, thereby illustrating that the membrane lipid can shield the strong interaction between the positively charged nanoplastics and cells. Conclusions Our findings elucidated the molecular mechanism of nanoplastics’ interaction and accumulation within bacteria, and implied the shielding and internalization effect of membrane lipid on toxic nanoplastics could promote bacteria for potential plastic bioremediation. Graphical Abstract

Acyl-coenzyme A: cholesterol acyltransferases are enzymes which are involved in the homeostasis of cholesterol. Impaired enzyme activity is associated with the occurrence of various diseases like Alzheimer's disease, atherosclerosis, and cancers. At present, mitotane is the only inhibitor of this class of enzymes in clinical use for the treatment of adrenocortical carcinoma but associated with common and severe adverse effects. The therapeutic effect of mitotane depends on its interaction with cellular membranes. The search for less toxic but equally effective compounds is hampered by an incomplete understanding of these biophysical properties. In the present study, the interaction of the three ACAT inhibitors nevanimibe, Sandoz 58-035, and AZD 3988 with membranes has been investigated using lipid model membranes in conjunction with biophysical experimental (NMR, ESR, fluorescence) and theoretical (MD simulations) approaches. The data show, that the drugs (i) incorporate into lipid membranes, (ii) differently influence the structure of lipid membranes; (iii) affect membrane structure depending on the lipid composition; and (iv) do not cause hemolysis of red blood cells. The results are discussed with regard to the use of the drugs, in particular to better understand their efficacy and possible side effects. [Display omitted] • The interaction of inhibitors of ACATs with membranes is investigated. • The drugs AZD 3988, nevanimibe and Sandoz 58-035 incorporate into lipid membranes. • The drugs differently influence the structure of lipid membranes. • The impact of the drugs on lipid membrane structure depends on the lipid composition. • The drugs do not cause hemolysis of red blood cells. [ABSTRACT FROM AUTHOR]